getCommand has been added, to use start your method with getCommand(userInput)

Calculations.java

@@ -0,0 +1,83 @@
+import java.util.ArrayList;
+
+public class Calculations
+{
+    public static ArrayList<String> library = new ArrayList<String>();
+    
+    public Calculations(){
+   
+    library.add("multiply");
+    library.add("divide");
+    library.add("subtract");
+    library.add("add");
+    library.add("COS");
+    library.add("SIN");
+    library.add("TAN");
+    library.add("invertS");
+    library.add("invertN");
+    library.add("factorial");
+    library.add("switchunit");
+    library.add("clear");
+    library.add("storeM");
+    library.add("resetM");
+    library.add("recallM");
+    library.add("displayM");
+        
+    }
+
+    public static String getCommand(String userInput)
+    {
+        boolean foundCommand = false;
+        String command = "";
+        String[] inputArr = userInput.split(" ");
+        for(int i = 0; i < library.size(); i ++)
+        {
+            String currCommand = library.get(i);
+            if(currCommand.equalsIgnoreCase(inputArr[0]))
+            {
+                command = currCommand;
+                foundCommand = true;
+                break;
+            }
+        }
+        
+        switch(command)
+        {
+            case "multiply":
+                Multiply(userInput);
+            break;
+            
+            case "divide":
+                Divide(userInput);
+            break;
+            
+            case "add":
+                Add(userInput);
+            break;
+            
+            case "subtract":
+                Subtract(userInput);
+            break;
+            
+            case "invertS":
+                InvertSign(userInput);
+            break;
+            
+            case "invertN":
+                InvertNumber(userInput);
+            break;   
+            
+            case "clear":
+                Clear();
+            break;
+        }
+        
+        return null;
+    }
+    
+    public static String InvertSign(String userInput)
+    {
+        
+    }
+   
+}

Console.java

@@ -7,26 +7,27 @@ import java.util.Scanner;
  */
 public class Console {
 
-    public static void print(String output, Object... args) {
-        System.out.printf(output, args);
-    }
+    
+    //public static void print(String output, Object... args) {
+    //    System.out.printf(output, args);
+    //}
 
-    public static void println(String output, Object... args) {
-        print(output + "\n", args);
-    }
+    //public static void println(String output, Object... args) {
+    //    print(output + "\n", args);
+    //}
 
-    public static String getStringInput(String prompt) {
-        Scanner scanner = new Scanner(System.in);
-        println(prompt);
-        String userInput = scanner.nextLine();
-        return userInput;
-    }
+    //public static String getStringInput(String prompt) {
+    //    Scanner scanner = new Scanner(System.in);
+    //    println(prompt);
+    //    String userInput = scanner.nextLine();
+    //    return userInput;
+    //}
 
-    public static Integer getIntegerInput(String prompt) {
-        return null;
-    }
+    //public static Integer getIntegerInput(String prompt) {
+    //    return null;
+    //}
 
-    public static Double getDoubleInput(String prompt) {
-        return null;
-    }
+    //public static Double getDoubleInput(String prompt) {
+    //    return null;
+    //}
 }

MainApplication.java

@@ -5,13 +5,13 @@
  */
 public class MainApplication {
     public static void main(String[] args) {
-        Console.println("Welcome to my calculator!");
-        String s = Console.getStringInput("Enter a string");
-        Integer i = Console.getIntegerInput("Enter an integer");
-        Double d = Console.getDoubleInput("Enter a double.");
+        //Console.println("Welcome to my calculator!");
+        //String s = Console.getStringInput("Enter a string");
+        //Integer i = Console.getIntegerInput("Enter an integer");
+        //Double d = Console.getDoubleInput("Enter a double.");
 
-        Console.println("The user input %s as a string", s);
-        Console.println("The user input %s as a integer", i);
-        Console.println("The user input %s as a d", d);
+        //Console.println("The user input %s as a string", s);
+        //Console.println("The user input %s as a integer", i);
+        //Console.println("The user input %s as a d", d);
     }
 }

package.bluej

@@ -1,23 +1,20 @@
 #BlueJ package file
-dependency1.from=MainApplication
-dependency1.to=Console
-dependency1.type=UsesDependency
-editor.fx.0.height=722
+editor.fx.0.height=717
 editor.fx.0.width=800
-editor.fx.0.x=640
-editor.fx.0.y=23
-objectbench.height=214
+editor.fx.0.x=497
+editor.fx.0.y=-827
+objectbench.height=200
 objectbench.width=595
 package.divider.horizontal=0.6
-package.divider.vertical=0.6847360912981455
-package.editor.height=473
+package.divider.vertical=0.6854103343465046
+package.editor.height=444
 package.editor.width=493
 package.editor.x=35
-package.editor.y=60
-package.frame.height=759
+package.editor.y=23
+package.frame.height=716
 package.frame.width=619
-package.numDependencies=1
-package.numTargets=2
+package.numDependencies=0
+package.numTargets=3
 package.showExtends=true
 package.showUses=true
 project.charset=UTF-8
@@ -27,16 +24,23 @@ readme.width=47
 readme.x=10
 readme.y=10
 target1.height=50
-target1.name=Console
+target1.name=Calculations
 target1.showInterface=false
 target1.type=ClassTarget
-target1.width=80
-target1.x=80
-target1.y=200
+target1.width=100
+target1.x=120
+target1.y=150
 target2.height=50
-target2.name=MainApplication
+target2.name=Console
 target2.showInterface=false
 target2.type=ClassTarget
-target2.width=120
-target2.x=70
-target2.y=70
+target2.width=80
+target2.x=20
+target2.y=150
+target3.height=50
+target3.name=MainApplication
+target3.showInterface=false
+target3.type=ClassTarget
+target3.width=120
+target3.x=70
+target3.y=70